The spread of cells from a solid tumor to remote sites in the body, a process known as metastasis, is responsible for over 90% of all cancer-related deaths. Cells originating from the primary tumor can enter the circulatory system and extravagate to invade, colonize, and proliferate in organs and tissues far from the primary neoplasm. Thus, the detection of these circulating tumor cells (CTCs) provides an invaluable opportunity for both the early identification and therapeutic targeting of metastatic cancer cells (Cristofanilli, 2004; de Bono, 2008). Current techniques for detection of CTCs include reverse transcriptase-polymerase chain reaction (RT-PCR), flow cytometry, fluorescence in situ hybridization, and, more recently, microfluidics. Unfortunately, RT-PCR does not distinguish between viable metastatic CTC versus nucleic acids or cellular fragments originating from the primary tumor.
Antibody-based techniques cannot be used for detection of all cancers, but only those cancers that express the most common and well-characterized markers. CTC enumeration of current systems only provides one layer of information regarding cancer diagnosis. One device, CellSearch® (Veridex, Raridan N.J.), has demonstrated commercial success for CTC analysis and is FDA approved for breast, prostate, and colon, while ovarian, rectum, and lung await approval. Limitations of the CellSearch® system include: (a) dependence on the level of EpCAM expression (Punnoose E A, et al., PLoS ONE. 2010; 5(9):e12517), (b) no use of mesenchymal markers (Punnoose E A, et al., PLoS ONE. 2010; 5(9):e12517), (c) reliance on antibody affinity for capture (Nagrath S, et al., Nature, 2007; 450(7173):1235-9.18097410), and most importantly (d) the absence of CTC phenotypic characterization.
There is no antibody that is 100% tumor or tissue specific and antibodies bind to viable as well as dead CTCs. Thus there is a need for a more sensitive, specific, and widely applicable technology for detection of rare CTC in blood. Further, there is a desperate need to develop new diagnostic agents and tools that not only detect and capture CTCs but also quantify their malignant potential and identify ‘up-front’ the therapies that are most effective in ablating an individual patient's tumor.
Despite the complexity and variability of cancers at a genome scale, a unifying theme is their growth deregulation phenotypes, the so-called hallmarks of cancer, which are conferred by mutations in a relatively small number of key pathways. Rather than focus on detecting individual genetic lesions that are numerous and highly variable between tumors, Applicants created diagnostic viruses that incorporate multiple transcriptional and molecular modules in their genomes to infect and detect a patient's tumor, report its molecular ‘hallmarks’ and its response to different therapies ‘up-front’. Using these agents, the molecular lesions and malignant characteristics of any given tumor can be rapidly discerned (within 24 hours) and scored via a standardized automated-platform. Furthermore, these agents could also be used as reporters to determine rapidly and directly if a patient's tumor is likely to respond to a particular therapy.